The present invention is particularly related to puffer-type circuit-interrupters of the type in which only a single pressure is utilized within the interrupting structure, and a difference of pressure for arc interruption is achieved by piston action, that is, relative movement of an operating cylinder to a piston structure. As well known by those skilled in the art, the relative motion between the operating cylinder and the piston achieves a desirable compression of gas within the compression chamber, which gas is utilized during arc interruption by generally forcing the high-pressure gas through a hollow nozzle structure to direct the high pressure gas flow intimately into engagement with the established arc to effect the latter's extinction.